/**
 * Created by Maibenben on 2017/5/12.
 */
function lazyload(callback) {
    var a = 0;
    var b = 0;
    var c = 0;
    var d = 0;
    window.addEventListener("touchstart", function (e) {
        a = e.touches[0].clientY;
        d = window.scrollY;
    });
    window.addEventListener("touchmove", function (e) {
        b = e.touches[0].clientY;
        c = b - a;
    });
    window.addEventListener("touchend", function () {
        if (c < -50 && (d - window.scrollY) == 0) {
            if (typeof(callback) == "function") {
                callback();
                a = 0;
                b = 0;
                c = 0;
            } else {
                return false;
            }
        }
    })
}
